1. Field of the Invention
This invention relates to large material handling systems; more particularly, it relates to a system and method for unstowing and stowing a crane boom assembly relative to a superstructure mounted on the bed of a mobile crane.
A large mobile crane of the type with which the present invention is concerned typically includes a telescoping boom assembly having two or more extensible and retractable boom sections nested within a boom base section which is pivotably mounted on the superstructure of the crane.
In operation, the boom assembly is mounted on the superstructure for rotation about a horizontal axis. The telescoping boom assembly may be rotated to and locked at a potentially infinite number of inclined working positions which range from 0.degree. to 80.degree. with respect to the horizontal. The angle of inclination determines the height to which loads may be raised by the boom assembly. Typically, one or more nested telescoping sections of the boom assembly may be extended outwardly to further increase the working height of the boom.
When the boom is not in use, the boom sections are fully retracted to facilitate storage. However, with the boom assembly mounted on the superstructure, cranes of the size and weight considered herein commonly exceed the maximum length limit permitted on public highways. Thus, when it is necessary to transport the crane from one job site to another, it has been necessary to remove the boom assembly or a portion thereof from the superstructure for transport on a separate vehcile in order to avoid exceeding the maximum length limits permitted on public highways.
2. Known Systems
Typically, boom assemblies of the length and weight considered herein have been constructed in boom sections having divisible halves. Thus the boom assembly itself must be physically disassembled each time the boom is to be moved to a new job site. Two transport vehicles are necessary to carry the separable halves of the boom assembly to the new job site, and the boom must be re-assembled at the new job site.
A boom assembly of the length and weight considered herein may be of unitary construction. In such a instance it would normally be necessary to detach the boom assembly from the superstructure to meet maximum length requirements for public highways. Further, such boom assemblies would have to be transferred from the vehicle carrying the superstructure to a second vehicle for transport to the new job site. At the new job site, the boom assembly would have to be manually re-connected to the superstructure for operation of the crane. Further, the main pivot means between the boom and the superstructure, as well as winches, masts, cable assemblies and related apparatus necessary for the working operation of the crane would have to be manually disconnected and reconnected each time the crane is transported from place to place.
Thus it would be desirable if a system and method were provided which would enable the stowage of such a crane boom and its associated superstructure on a single transport vehicle.
Futher, it would be desirable if the boom assembly could be stowed and unstowed by means of an automatic system, to eliminate the manual disconnection and re-connection of the boom assembly and the superstructure, with resultant savings in stowage and unstowage time, and to reduce the necessity of contact of associated personnel with the crane assembly during the stowage and unstowage procedures, with resultant savings in manpower requirements.
Futher, it would be desirable to eliminate the need to disconnect winches, masts, cables and related apparatus necessary for the working operation of the crane when the boom assembly is stowed. To keep such apparatus in operative engagement with the boom assembly during the stowage period substantially decreases the setup time at the new job site, and virtually eliminates the human error inherent in the manual reconnection of such apparatus at the new job site.
Further, it would be desirable to provide positive locking means for securing the boom to the superstructure when the boom is mounted in the unstowed or inclined working position, to insure that the boom is locked to the superstructure when the boom is raised to the inclined working position.
The object of the present invention is to provide an improved system and method for unstowing and stowing the boom assembly associated with a crane superstructure.
A further object of the present invention is to provide a method for automatic unstowing and stowing of the telescoping boom assembly of a crane.
A further object of the present invention is to provide an improved system and method of unstowing and stowing the telescoping boom assembly of a material handling apparatus, the method eliminating the connection and disconnection of apparatus associated with the operation of the crane boom during the unstowing and stowing process.
Another object of the present invention is to provide positive locking means between the boom and the superstructure, when the boom is unstowed to an inclined or working position, to insure that the boom is locked to the superstructure when the boom is raised to a working position.